Hydraulic mechanism



June 16, 1942.

T. BROWN HYDRAULIC MECHANISM Filed Feb. 7, 1941 2 Sheets-Sheet 1 FIG. I

A TTORNEYS.

June 16, 1942. T. BROWN HYDRAULIC MECHANISM Filed Feb. 7, 1941 2Sheets-Sheet 2 INVE OR:

ATTORNEYS.

FIG. 4

Patented June 16, 1942 & Company, nois Moline, 111., a corporation of1111- Application February 7, 1941, Serial No. 377,838

14 Claims.

The present invention relates generally to hydraulic mechanisms and moreparticularly to a new and improved hydraulic mechanism for tractors andthe like for use as power lift mechanism therefor, and is in the natureof an improvement over the hydraulic mechanism shown and described inPatent 2,107,760, granted February 8, 1938 to McCormick et al.

The mechanism disclosed in the above-mentioned patent comprises a footpedal control for a hydraulic type power lift, so arranged andconstructed that a single actuation of a foot pedal causes a movement ofthe piston in the cylinder over a fixed range, and in which the valvemechanism is shifted back to a neutral position to stop the piston atthe end of its range. This operation can be applied to lift a groundengaging implement to a transport position on the tractor. .A secondactuation of the foot pedal causes the piston to travel back to theoriginal position to return the implement to the ground. Thischaracteristic, of performing a complete cycle of operation upon asingle actuation, without further attention from the operator, isdesirable in certain farming operations such as cultivating, for whenthe tractor reaches the end of a row, the implements must be raised, thetractor turned sharply around, and the implements again lowered, all ina very short time, so that any unnecessary operations or the necessityfor accurate adjustments, would greatly interfere with the control ofthe tractor.

Inasmuch as a power lift piston using this type of control has a fixedrange of operation, adjustments in depth of operation must be made byexternal linkages between the piston and the implements. Although powerlift mechanisms are known in the art, which have double acting pistonsadapted to force implements down to any desired depth and hold them insuch position, this must be accurately adjusted by hand each time thatthe implements are lowered from transport position.

It is the principal object of the present invention to provide a powerlift mechanism which can be adjusted to a predetermined range of stroke,and after having once been adjusted, the piston always returns to thesame desired terminal position upon subsequent actuations of a footpedal or other control element. A manual control lever isprovided foradjusting the position of the cylinder from the predetermined terminalposition and at the same time starting the automatic mechanism so thatupon subsequent operations of the piston, it will return to the newlydetermined terminal position. A further object relates to the provisionof a mechanism in which the position of the foot pedal or correspondingcontrol element is not affected by adjustments of the piston by means ofthe manual control lever.

These and other objects and advantages of my invention will be apparentto those skilled in the art after a consideration of the followingdescription, in which reference is had to the drawings appended hereto,in which:

Figure 1 is a side elevational view of a hydraulic control mechanismembodying the principles of my invention;

Figure 2 is an end elevational view of the mechanism shown in Figure 1;

Figure 3 is an end elevational view of the ratchet mechanism as viewedalong a line 33 in Figure 2; and

Figure 4 is an elevational view taken in section through the hydrauliccontrol valve and drawn to an enlarged scale.

Referring now to the drawings, reference numeral 5 indicates a mainsupport, which can be a tractor or any other suitable vehicular orstationary support for a hydraulic cylinder 6 dis;

posed in a horizontal position and within which .is slidably disposed apiston 6 adapted to travel from one end of the cylinder 6 to the other.The piston is mounted on a piston rod 1 which extends out of thecylinder 6 through a suitable fluid-tight gland or bearing 8 at one endthereof. The piston rod I is connected by means of suitable link 9 to anarm in mounted on a rock shaft l I, which is journaled in a supportingbearing l2 fixed to the side of the support 5. The rockshaft II can beconnected in any desired manner to raise and lower or otherwisemanipulate an implement or the like associated therewith. Such implementconnection is represented by a rod 13 having an upper end journaled on apin l4 attached to 'the arm l0. By swinging the latter in a clockwisedirection, the implement can be raised by force transmitted through therod l3, and the implement can be forced into the ground by rocking thearm I in a counterclockwise direction. The piston is forced from rightto left in the cylinder 6, as viewed in Figure 1, by introducing oilunder pressure through a duct l5 connected in communication with one endof the closed cylinder 6, and the piston is forced from left to right,as viewed in Figure l, by introducing oil under pressure through a ductI6 connected in communication with the opposite end of the cylinder 6.The oil or other fluid is controlled by means of a valve ll comprising acylinder casing i8 fixed by any suitable means to the side of thesupport 5. The casing l8 provides a valve chamber l9 within which isrotatably disposed a movable valve member 20, which is rotatable withinthe casing but which fits tightly enough to prevent oil from leakingaround the edges of the valve member. The oil ducts l5, l6 are connectedin communication with the valve chamber l3 at diametrically oppositesides of the casing I 3, and a second' pair of ducts 2|, 22 areconnected at opposite sides of the valve casing in communication withthe chamber l9 and disposed on an axis substantially at right angles tothe axis of the valve ducts l5, IS. The lower duct 2| is connected tothe discharge end of a suitable hydraulic pump (not shown), which can beof any suitable type such as the gear type of pump shown in theaforementioned patent. The upper duct 22 is connected to the intake sideof the hydraulic pump. The rotatable valve member 20 is provided with apassage 23 therethrough, which passage is disposed in register with thehigh and low pressure ducts 2|, 22 of the pump, when the valve member isin a neutral position, as shown in Figure 3, thus providing a by-passfor the oil flowing from the pump to the valve, through the passage 23and returning through the return duct 22 to the pump. The valve member20 also serves as a barrier between the two cylinder ducts l5, l6,thereby locking the fluid in the opposite ends of the cylinder andpreventing any movement of the piston within the cylinder.

By rotating the valve member 20 to the position indicated by A in Figure4, the discharge duct 2| from the pump is connected in communicationwith the cylinder duct l6, whereby oil under pressure is forced into theleft end of the cylinder and thus exerting a pressure upon the pistontending to force the same toward the right, as viewed in Figure 1. Inposition A of the valve member20,the other cylinder duct |is connectedin communication with the return duct 22 to the pump and thus permittingoil to flow from the right hand end of the cylinder 6 through the returnduct 22 and back to the pump. The piston can be stopped in anyintermediate position in the cylinder 6 by returning the valve member toits neutral position, shown in solid lines in Figure 3, and will belocked in that position, as described above.

The rotatable valve member 20 is shifted by means of a shaft 25connected thereto and extending axially out of the cylindrical casing l3through a suitable oil-tight bearing 26. Rigidly fixed to the shaft 25is a valve control lever 30, which extends vertically upward in theneutral position of the valve member 20.. The upper end of the lever isprovided with a handle 3| by means of which the lever 30 may be rockedmanually about the axis of the shaft 25. Thus, the lever 30 is rockedtoward the left, as viewed in Figure 1, to cause the piston and pistonrod 1 to move toward the right, and is rocked toward the right from thevertical position to effect a movement of the piston toward the left inthe cylinder.

To return the valve lever 30 to a vertical neutralposition at the end ofa power stroke of the piston, I have provided a valve control rod 33pivotally connected by means of a pin 34 to the end of the rock shaftarm 10, and slidably supported at its opposite end in a yoke member 35which is pivotaliy supported on the valve lever 33 on a pair oftrunnions 36, 31, extending from opposite sides of the yoke member 35.

- The trunnion 38 is .iournaled in the valve lever 30 and the trunnion31 is journaled in a hammer strap 38, which is fixed in a verticalposition on the lever 30 and bent outwardly to embrace the yoke 35. Thelatter is provided with a central aperture 39 through which the valvecontrol rod 33 extends and is slidably supported therein. Thus, as thepiston rod I moves from one end of the cylinder toward the other, thevalve control rod 33 slides through the yoke 35 by virtue of itsconnection with the piston rod 1.

An adjustable sto member 43 is mounted on the outer end of the valve rod33 and has an aperture 4| extending therethrough to receive the rod 33.The lower side of the aperture 4| is provided with a series of teeth 42,which are adapted to interfit with rack teeth 43 provided'on the bottomof the control rod 33, for the purpose of preventing the stop member 40from sliding axially along the rod 33. The teeth 42, 43 are held inengagement by means of a spring 44, which is disposed in the upper partof the aperture 4| above the valve rod 33 and tends to urge the stopmember 40 upwardly to bring the teeth into engagement. The stop member40 can .be set at any desired point near the outer end of the controlrod 33 and is then adapted to move with the piston rod 1 duringoperation of the latter.

When it is desired to lower the implements to a predetermined depth inthe ground, the control lever 30 is moved toward the right, as viewed inFigure 1, thus efiecting a movement toward the left of the piston rod 1and the valve control rod 33, until the stop member 40 engages the endof the yoke 35, whereupon further movement of the piston causes thelever 30 to be moved back to a vertical or neutral position and thusstopping the piston. By moving the stop member 40 outwardly toward theend of the rod 33, the length of stroke of the piston rod I can beincreased and thereby increasing the depth of operation of thecultivator or other implement connected thereto, and similarly by movingthe adjustable stop 40 to the left along the rod 33, the valve lever 30can be made to return to neutral position earlier in the stroke of thepiston, and thus reduce the length of stroke and consequently the depthof operation of the implement. Figure 1 illustrates the relativepositions of the parts during operation of the implement. It will benoted that the adjustable stop 40 is in contact with the yoke 35, havingengaged the latter to swing the control lever 30 into the presentvertical position.

In the raising stroke of the piston, the valve control lever 30 is swungtoward the left, as viewed in Figure 1, thereby effecting a movement ofthe piston rod 1 and valve control rod 33 toward the right. A secondstop member 43 engages the opposite end of the yoke 35 during theraising stroke to return the valve control lever 30 to neutral positionto stop the piston at the end of such stroke. Inasmuch as it is notnecessary to frequently adjust the upper limit of the movement of theimplement, the stop 48 comprises merely a bolt which is inserted througha suitable aperture in the valve control rod 33 and serves the purposeof engaging the yoke 35. It is occasionally desirable, however, tochange the upper limit of the raising movement of the implement,inasmuch as some implements require greater clearance to avoid The latcharm 50 is in the form of a bail, one end of which is pivotally connectedto the hammer strap 38 on a pivot bearing 5|, and from which the bail 50extends around the lever 38 to a second pivot bearing 52, which issupported on a latch box 53 fixed to the outer side of the lever 30. Thebail 50 extends beyond the pivot 52 to 5 provide an actuating armportion 54, the outer end of which is connected by a link 55 to avertically extending latch bolt 56, disposed generally parallel to thevalve lever 38 and supported for vertical sliding movement in the latchbox 53 and in a bearing support 51 spaced vertically therefrom. Thelatch bolt 56 is urged downwardly by means of a compression spring 58coiled about the bolt and abutting the under side of the bearing block51. The lower end of the spring 58 acts against a flange 59 fixed to thebolt 56. The flange 59 also acts against the latch box 53 to provide astop for the downward movement of the latch bolt 56. The upper end ofthe latch bolt 56 is turned outwardly to provide a handle 60 adjacentthe lever handle 3|, which can be gripped with the latter when the valvelever 38 is actuated. By raising the handle 60 the extension 54 of thelatch arm50 is raised through the link 55, thus moving the baildo'wnwardly into engagement with the top of the adjustable stop member40; the latter being formed to provide a recess 6| adapted to receive adownwardly projecting latch finger 62 formed on the lower side of thelatch bail 50. Upward pressure against the handle 60 causes the bail toforce the adjustable stop member 48 downwardly against the spring 44 todisengage the teeth 42 from the rack 43 on the control rod 33, afterwhich the valve lever 30 can be swung to control movement of the pistonin the cylinder 6. When the piston has been adjusted to the desiredposition, the lever 30 is returned to a neutral position and the handle60 is then released, which allows the spring 58 to force the latchbolt56 downwardly and thus releasing the latch finger 62 from the notch 6|in the adjustable stop member 40, whereupon the latter is again lockedin place on the valve rod 33 by means of the teeth 42, 43. Since theadjustable stop 40 is fixed to the valve lever 38 by means of the latcharm 50 during control movements of the lever, the valve rod 33 slidesthrough the .stop member 40 during movement of the piston rod I, so thatin the finally adjusted position the stop member 40 is in a new positionon the valve rod 33 in abutment with the yoke 35 and thus establishes anew terminal position ofthe piston rod I, to which the latter willreturn during subsequent movements thereof.

The valve lever 30, however, is used only for making adjustments fromthe predetermined lowered terminal position of the piston, while thecontrol for normally raising and lowering the implement during operationis effected by mechanism which will now be described.

A second control element in the form of a lever all section 65 isprovided with a hub 66, which is journaled on a stub shaft 61, thelatter being preferably formed integrally with the valve control lever38 and disposed coaxially with the valve shaft 25. Thus, the leversection 65 and the valve lever 38 are swingable about the same axis ofrotation and are normally locked together by means of an extension 68 ofthe latch bolt 56 which projects below'the latch box 53 into a centrallydisposed notch 69 in an arcuate sector I0, which is formed integrallywith the hub 66 and extends upwardly therefrom. The length of the boltextension 68 is such that when the valve lever 30 is out of its neutralposition and the bolt 56 is withdrawmthe lower end of the bolt extension68 slides on the arcuate surface of the sector "and thus holds the bolt56 in raised position and the latch finger 62 in engagement with thenotch 6| ,thus insuring that the stop member 40 will be retained inconnection with the lever 30 during manual adjustment of the piston. I

The control lever section 65 is connected by means of a link rod II to acrank arm I2 fixed to a rotary ratchet member I3. The ratchet member 13is rotatably supported on a stub shaft I4, which is suitablycarried bythe support 5.

Joumaled on the shaft I4 is a ratchet crank I6, the outer end of whichcarries a pivot pin 11, on which is journaled a ratchet dog I8. The endof the ratchet arm I6 is also curved to provide a rigid abutment arm I9for supporting a compression spring 88 which acts against the ratchetdog I8 to force it into engagement with the outer camming edge of theratchet member I3, the latter being provided with notches 8| adapted toengage the end of the ratchet dog I8. The ratchet arm I6 is swungthrough a definite arc by means of a foot pedal 85, which is rigidlyfixed to a rock shaft 86 supported in laterally spaced bearings 81 ontop of the main support 5. An actuating arm 88 is fixed to the outer endof the rock shaft 86 and is connected bymeans of a link 89 to the pin 11on the end of the ratchet 'arm I6. The foot pedal 85 is normally held inraised position by means of a coil spring 98 which encircles the rockshaft 86 and acts against the lower side-of the foot pedal and reactsagainst the bearing 81. A short stop arm 9| is provided on the footpedal for limiting the upward movement of the latter by engaging themain support 5 when the pedal is in raised position. The main support 5provides a limit for the foot pedal when till tltig latter is actuateddownwardly by the opera r.

Pressing the foot pedal downwardly against the main support 5 raises theratchet arm I6 through the arm 88 and link 89 and thus causes theratchet member I3 to be rotated approximately a quarter of a revolutionin a clockwise direction as viewed in Figure 1, by force transmittedthrough the ratchet dog I8 against one of the notches 8|. This rotatesthe crank arm I2 through approximately a quarter of a revolution andthus swings the lever section 65 by means of the connecting link I|through a defmite angle about its axis of rotation. By virtue of theconnection between the latch bolt 68 and the notch 69, the valve controllever 38 is swung with the lever section 65 and thus opens the controlvalve to effect a movement of the piston in the cylinder 6. Thus,movement of the crank arm I2 through a quarter of a revolution from theposition shown in Figure 1, will move the lever section 65 toward theright, and the control lever 30 toward the left, therefore effecting amovement of the piston rod I and valve control rod 38 toward the rightto raise the implement until the stop 48 engages the yoke 35 and returnsthe lever to neutral position. When the valve lever is returned toneutral position the ratchet member I3 is rotated by means of the linkII and arm I2 through another approximate quarter of a revolution andthus bringing the arm I2 to the lower side of the ratchet member 13.During this movement of the latter, the ratchet dog I8 slides on thecamming surface of the member I3 and then slips into the succeedingnotch 8I' in the member 13 in readiness for another actuation by meansof the foot pedal 85. This actuation rotates the arm I2 in a directionaway from the lever 85, pulling the latter through the link II andswinging the valve lever 30 toward the right. The lever 30 is returnedonce again to neutral position when the stop member 40 engages the same,and this effects a fourth quarter revolution of the ratchet member I3 toreturn the same to the position shown in Figure 1.

It will be noted that when the lever section 65 is in either of itsextreme positions, the crank arm 12 is in a slightly over-centerposition with respect to the shaft 14. This insures that when the leversection 65 is returned to central position, the ratchet member I3 willbe rotated progressively in the same direction of rotation, thusavoiding a dead-center locking condition between the crank 12 and linkII. Since the top and bottom positions of the arm 12 are necessarily onthe right hand side of the center line, the notchBI must becorrespondingly greater than 180 degrees behind notch 8I, as indicated.The levers 30, 55 are retained in vertical or neutral position and inboth extreme positions by means of a roller I carried at the lower endof the lever section 65 and disposed to roll upon a track IOI which issupported on a bracket I02 fixed to the side of the main support 5. Theroller I00 is provided with a shaft I03, which projects through avertical slot I04 in the lower end of the lever 65. The roller I00 isurged against the track IN by means of a spring biased toggle mechanismcomprising a pair of upwardly diverging links I05, I08 journaled on theshaft !03 at each side of the roller I00 and connected at theirupperends to a pair of pins I01. A pair of links I08 are journaled at theirlower ends on the pins I01 between the front and rear links I05, I06 andhave outwardly turned upper ends I09 which are pivotally connected tothe lever section 65. The two pins I01 are interconnected by a tensioncoil spring I I0 tending to force the pins I01 together and thus pressthe roller I00 downwardly against the track IN. The track IN is in theform of a circular are having as its center the axis of rotation of thelever 65, and is provided with a recess III at the center thereofadapted to receive the roller I00 when the levers 30, 85 are in verticalneutral position. The spring IIO must be extended slightly in order toswing the lever 65 in either direction from the neutral position, andthus the spring serves to yieldably retain the lever in said neutralposition. Each end of the arcuate track IOI is provided with a recessH2, H3 into which the roller I00 seats when the lever 65 is in eitherextreme position, and thus holding it in that position until the leveris engaged by o of the stop members 40, 48 to return it to neutral.

i wing the operation of the mechamsm,

which is shown in the drawings as in the position in which theimplements are lowered to a predetermined operating depth in the ground,the implements are raised by stepping on the control pedal 85, causingthe ratchet dog I8 to move the ratchet member I3 a quarter of arevolution in a clockwise direction, and thus acting through the link 1|to swing the lever section 55 and valve lever 30 in a counterclockwisedirection in which the roller I00 drops into the recess II2,corresponding to position A of the valve member 20, as illustrated inFigure 3. This connects the high pressure duct 2| with the cylinder ductI8, forcing the piston to the right and rocking the rock shaft II in aclockwise direction until the stop 48 engages the yoke and returns thelevers to a vertical position, and swinging the crank 12 downwardlysomething less than a quarter of a revolution. A second actuation of thefoot pedal 85 rotates the ratchet member 13 slightly more than a quarterof a revolution and this pulls the lever section 55 and control lever 30in a clockwise direction, dropping the roller I 00 into the notch H3 andsetting the valve member 20 in a reverse posiiion in which the cylinderduct I5 is connected with the high pressure pump conduit 2|. Thiseffects a movement of the piston toward the left,

thereby rocking the rock shaft II in a counterclockwise direction untilthe stop member 40 engages the yoke 35 and pushes the lever back to avertical position.

Assuming now that it is desired to adjust the implement to a slightlylower working position, the latch handle 60 is raised, thus raising thelower end of the bolt 58 out of the notch 69 and forcing the latch arm50 into the notch SI and pushing the stop member 40 downwardly againstthe action of the spring 44 until the teeth 42, 43 are disengaged. Thevalve lever 30 is now free to move independent of the lower leversection 65, and by swinging the lever 30 to the right the valve member20 is turned in a clockwise direction until oil is forced under pressurethrough duct I5 and forcing the piston and piston rod I toward the left,thus forcing the implements deeper into the ground. When the desireddepth has been attained the lever 30 is restored to a vertical positionand the handle 60 released, thereby relocking the bolt 58 into the notch69 and also restoring the teeth 42, 43 into interengagement to securethe adjustable stop in fixed relation to the rod 33. The next actuationof the foot pedal 85 effects a movement of the piston to the right toraise the implement to the same position in which it was previouslyraised, with the stop 48 against the valve lever 30, but upon the nextactuation of the foot pedal 85 the implement returns to the newoperating depth by virtue of the fact that the adjustable stop 40 is nowin a different location upon the valve rod 33, causing the piston tomove a slightly greater distance in the cylinder 8 than in the previousactuation of the foot control. If it is desired to raise the implementsto a greater height, the stop bolt 48 is moved to an aperture 49 spacedto the left of its present position, and if it is desired to decreasethe height to which the implement is raised, the bolt 48 is moved to anaperture 49 spaced to the right of the present location.

I do not intend my invention to be limited to the details of theembodiment shown and described herein, except as speciflcally limited bythe terms of the claims which follow.

able therewith into engagement with said control lever to shift thelatter back to said neutral position to stop said movable member in aoertain terminal position, said stop being shiftable relative to thelatter to adjustthe terminal position thereof, and a latch carried bysaid control lever and engageable with said stop for shifting the latterwith said lever.

2. In a hydraulic mechanism, the combination of a cylinder and a pistonmovable relatively therein, a control element associated therewith andshiftable from a neutral position to a definite position to effect amovement of said piston in said cylinder, means responsive to themovement of said piston to a predetermined terminal position forreturning said control element to said neutral position to hold saidpiston at said terminal position, an auxiliary control lever shiftableto adjust said piston from said terminal position, and means,cooperative with said piston movement responsive means, and responsivein turn to the adjustment of said piston, for determining a new terminalposition at which the piston is stopped during subsequent movementsthereof.

3. In a device of the class described, the combination of a poweractuated movable member,

a control element associated therewith and shiftable from a neutralposition through a definite range to effect a movement of said movablemember, means responsive to the movement of said member to apredetermined terminal position for returning said control element tosaid neutral position to stop said member, an auxiliary control levershiftable to adjust said movable member from said terminal position, andmeans, cooperative with said movement responsive means, and adjusted bysaid auxiliary control lever, to adjust said movement responsive meansand thereby determining a new terminal position at which said movablemember is stopped during subsequent movements thereof.

4. In a device of the class described, the combination of a poweractuated movable member, a control member associated therewith andhaving a first control lever shiftable from a neutral position to adefinite position to initiate a movement of said movable member, a pairof interengageable parts attached to said movable member and saidcontrol member, respectively, and movable therewith ifor returning thelatter to said neutral position responsive to movement of said movablemember into a predetermined terminal position, and thereby stopping thelatter, and a second control lever associated withsaid control memberfor adjusting said movable member from said predetermined terminalposition, said second control lever being connected to one of saidinterengageable parts for shifting the latter relative to the member towhich the part is attached, when said movable member is adjusted, todetermine a new terminal position at which said movable member isstopped responsive to engagement between said parts during subsequentmovements of said movable member initiated by said first control lever.

5. In a device of the class described, the combination of a poweractuated movable member, a

controlelement associated therewith and shiftable from a neutralposition through a definite range to effect a movement of said movablemember, a pair of interengageable parts attached to said movable memberand said control element, respectively, and movable therewith forreturning the latter to said neutral position responsive to movement ofsaid movable member into a predetermined terminal position, and therebystopping the latter, an auxiliary control lever shiftable to adjust saidmovable member from said terminal position, and means connected withsaid auxiliary control lever for shifting one of said interengageableparts when said movable member is adjusted, and thus establishing theadjusted position of the latter as a new terminal position at which saidmovable member is.

stopped during subsequent movements thereof.

6. In a hydraulic mechanism, the combination of a cylinder and a pistonmovable relatively therein, a control valve associated therewith andshiftable from a neutral position to effect a movement of said piston insaid cylinder, a

manually controlled lever for shifting said valve,

a control elementydetachably connected to said valve and movable from aneutral position to a definite-active position to actuate said valve, apair of interengageable stops attached to said piston and to said valve,respectively, to move therewith into engagement to actuate the latter tostop said piston in a predetermined terminal position, means fordetaching said valve from said control element to permit actuating thevalve independent thereof for adjusting said piston from said terminalposition, and means for adjusting one of said stops coincident with saidindependent valve actuation to establish the adjusted position of saidpiston as a new terminal position at which said piston'is automaticallystopped during subsequent movements thereof. '7. In a hydraulicmechanism, the combination of a cylinder and a piston movable relativelytherein, a control valve associated therewith and shiftable from aneutral position to effect a movement of said piston in said cylinder, amanually controlled lever for shifting said valve, a control element,latch means connecting the latter with said valve, said control elementbeing movable from a neutral position to a definite active position toactuate said valve, a pair of interengageable stops attached to saidpiston and to said valve, respectively, to move therewith intoengagement to actuate the latter to stop said piston in a predeterminedterminal position, a latch lever mounted on said manually controlledlever and operative to detach said control element from said valve topermit actuating the latter independent of said element for adjustingsaid piston from said terminal position, and means responsive to saidindependent movement of said manually controlled lever for adjusting oneof said stops to establish the adjusted position of said piston as a newterminal position at which said piston is automatically stopped duringsubsequent movements thereof.

8. In a hydraulic mechanism, the combination of a cylinder and a pistonmovable relatively therein, a control valve associated therewith andshiftable from a neutral position to effect a movement of said piston insaid cylinder, a manually controlled lever for shifting said valve, acontrol element, latch means connecting the latter with said valve, saidcontrol element being movable from a neutral position to a definiteactive position to actuate said valve, a pair of interengageingsubsequent movements thereof.

able stops attached to said piston and to said valve, respectively, tomove therewith into engagement to actuate the latter to stop said pistonin a predetermined terminal position, a latch lever mounted on saidmanually controlled lever and operative to detach said control elementfrom said valve to permit actuating the latter independent of saidelement for adjusting said piston from said terminal position, and meansresponsive to movement of said latch lever for shifting the stop,associated with said piston relative to the latter by means of saidmanually controlled valve -lever, said last mentioned stop beingreconnected to said piston upon release of said latch lever to establishthe adjusted position of said piston as a new terminal position at whichsaid piston is automatically stopped 9. In a device of the classdescribed, the combination of a power actuated movable member, a controlelement associated therewith and shiftable from a neutral positionthrough a definite range to effect a movement of said movable member, astop member detachably connected to said movable member to movetherewith into engagement with said control element to shift the latterback to said neutral position to stop said movable member in apredetermined terminal position, an auxiliary control lever shiftable toadjust said movable member from said terminal position, and a latchcontrolled by means carried on said lever, for engaging said stop memberto shift the latter with said lever and reconnect the stop after thepiston has been adjusted in position to determine a new terminalposition at which said.movable member is stopped during subsequentmovements thereof.

10. In a hydraulic mechanism, the combination of a cylinder and a pistonmovable relatively therein, a control valve associated therewith andshiftable from a neutral position to effect a movement of said piston insaid cylinder, a manually controlled lever for shifting said valve, andmounted for rocking movement and connected to said valve to shift thelatter, a second control lever mounted for independent rocking movementabout the same axis, a sector fixed to said second control lever andhaving a notch therein, a latch bolt slidably mounted on the firstmentioned lever and adapted to engage said notch to latchthe two leverstogether, a control rod attached to said piston for movement therewith,a stop member detachably fixed to said rod and movable into engagementwith dursaidcflrst control lever to shift the latter back to saidneutral position to stop said piston, and means responsive to movementof said latch bolt out of said notch for detaching said stop member fromsaid control rod and attaching the same to said lever to move therewith.

11. The combination set forth in claim 10 with the further provision ofa foot pedal operated ratchet mechanism for successively moving saidsecond control lever alternately in opposite directions to effectalternate movements of said piston in opposite directions.

12, In a device of the class described, a control member movable from aneutral position in either of two directions to definite activepositions, a unidirectionally operable step-by-step mechanism for movingsaid control member from said neutral position to said active positionsalternately upon successive actuations of said mechanism, and separatemeans for returning said control member to neutral position, saidmechanism including .'a crank member, link means connecting said crankmember with said control member, a control element, and means forangularly moving said crank member through unequal portions of arevolution during one complete cycle of movement of said crank uponactuations of equal extent of said control element.

13. In a device of the class described, the combination of a poweractuated movable member, a control element associated therewith andshiftable from a neutral position to effect a movement of said member ina certain direction, a stop supported for movement relative to saidcontrol element, the latter being engageable with said stop incident torelative movement therebetween, to limit the extent of movement of saidmember, and an adjusting device mounted on said control element, foradjusting the position of said stop, thereby changing the terminalposition of said member.

14.- In a device of the class described, the combination of a poweractuated movable member, a manually operable control lever associatedtherewith and shiftable from a neutral position to effect a movement ofsaid member in a certain direction, a stop engageable with said leverand operative to limit the extent of movement of said member, a handlemounted on said lever and movable relative thereto, and means foroptionally connecting said handle with said stop for shifting the latterand thereby changing the terminal position of said member.

